All the 1972 images in FBSharedFramework are inside the main Assets.car and also part of the FBNotOnStartupPathFramework Assets.car. So there are 3 times the same 1972 images taking 3 x 9.5 MB = 28.5 MB.

Keeping a single set of these 1972 images would save 19 MB.

The remaining images in the main Assets.car (2267 - 1972 = 295) and in the FBNotOnStartupPathFramework Assets.car (2126 - 1972 = 154) are unique.

New localizations

The Facebook.app gained 5 new localizations, increasing the app size by 4.2 MB:

hi.lproj (1.3 MB)

hr.lproj (692 KB)

hu.lproj (750 KB)

ro.lproj (709 KB)

sk.lproj (713 KB)

Also each localization got a new 12 KB file called AdsCountriesConfig.json. This adds 336 KB.

DO_NOT_USE_OR_YOU_WILL_BE_FIRED

When analyzing the version 66.0 I completely missed some amusing Objective-C interfaces, protocols and methods: